In general, this invention relates to apparatus for processing color video signals. More particularly, this invention relates to color video signal apparatus which includes a digital memory for storing a frame of a color video signal.
In many applications using color video displays, there exists a need for storing and processing frames of color video information. Thus in consumer video cassette recorder (VCR's), when a video signal is played back in a still frame mode, image degradation and decreased resolution result when the video head is used for reproducing images from video tape which has been recorded at one speed and played back when stopped. Image degradation results from the playback of video signals from adjacent tracks which are scanned by the rotating head. Poor image resolution results from the playback of a single field of a frame of color video information. Furthermore, in many applications it is desirable to process a frame of video information to achieve image enlargement or reduction, image rotation, superimposition of one image on another image, and the like. Such image processing techniques are unavailable in a VCR which only reproduces signals directly from the tape.
Providing a frame store for storing a frame of color video signals which may be repeatedly read out solves some of these problems but introduces other problems. In a frame store, it is desirable that sufficient video signal information is stored so as to display a reproduced image on a video monitor which accurately reflects the image resolution and color qualities of the original color video signal image. It is also desirable that the frame store and its associated analog-to-digital conversion circuitry be economical so that the frame store apparatus may be made more widely available to markets such as the consumer market. In digital frame stores where the composite color video signal has been sampled at high frequency sampling rates, (such as four times the frequency of the color subcarrier) the high speed analog-to-digital converter is expensive and produces a large number of digital samples for storage which increases the size and cost of the digital memory required. Similarly, a frame store which stores all three color component signals at full bandwidth requires three analog-to-digital converters and a large digital memory capacity thus increasing cost and complexity.